A photosensitive element including a layer formed from a photosensitive resin composition (hereinafter, referred to as “photosensitive layer”), a support film and a protective film has been conventionally widely used as a resist material for etching, plating and the like in the production field of a printed-wiring board and the high-precision processing field of metal.
The printed-wiring board is produced as follows, for example. First, the protective film of the photosensitive element is peeled from the photosensitive layer, and thereafter the photosensitive layer is laminated on a conductive film of a circuit-forming board. Then, the photosensitive layer is subjected to pattern exposure, thereafter an unexposed region is removed by a developing solution, and a resist pattern is formed. Then, an etching treatment or a plating treatment is conducted based on this resist pattern to pattern the conductive film, thereby forming the printed-wiring board.
As this developing solution used for removal of the unexposed region, an alkaline development type such as a sodium carbonate solution is mainly used. The developing solution may usually have the ability to dissolve the photosensitive layer, and the photosensitive layer is dissolved in the developing solution or dispersed in the developing solution during development.
In accordance with miniaturization of patterning of the conductive film in recent years, the photosensitive layer of the photosensitive element has been demanded to have excellent adhesiveness for the circuit-forming board and high resolution for resist pattern formation.
Usually, when a resist is formed using the photosensitive element, the photosensitive layer is laminated on the board and then exposed with the support film being not peeled. In order to address with such an exposure treatment, a light-permeable material may be adopted for the support film. In addition, in order to achieve a high resolution in pattern formation, the support film is required to be as thin as possible. On the other hand, in order to coat the support film with the photosensitive resin composition in a uniform thickness at a high yield, the support film is demanded to have a certain thickness (generally 10 μm to 30 μm). In addition, for the purpose of the enhancement in productivity of the support film, namely, the enhancement in winding property of the support film, the support film generally contains inorganic particles or organic particles. Therefore, the conventional support film has the following tendency: the haze thereof is increased, particles contained in the support film cause light scattering in exposure, and the photosensitive film cannot respond to a demand for a higher resolution.
As a method for achieving a higher resolution, there is a method in which the support film with which the photosensitive element is provided is peeled before exposure and exposure is conducted with no support film interposed. In this case, a phototool may directly adhere to the photosensitive layer. The photosensitive layer, however, usually has some level of adhesiveness, and thus the phototool adhering thereto is difficult to remove when the phototool directly adheres to the photosensitive layer and exposure is performed. In addition, the phototool is contaminated by the photosensitive layer and the support film is peeled to thereby cause the photosensitive layer to be exposed to oxygen in the air, easily resulting in a reduction in photosensitivity.
In order to overcome the above points, various measures have been proposed. For example, in JP 07-333853 A, WO 2000/079344 A and JP 4905465 B, the following has been proposed: the size of a particle included in a support film and the haze of the support film are within specific ranges to thereby allow a resist pattern excellent in resolution and the like to be formed.